The so-called anonymous communication is a communication to be performed in a situation in which a caller does not reveal identification information for specifying itself to the communication partner. As one example, there exists a caller number notification/non-notification service by an IP communication network using voice described in Non-patent literature 1. In this caller number notification/non-notification service, adopting the caller number non-notification as a default setting at the time of a contract, or affixing “184” to the head of a destination telephone number and dialing up with the caller device, for example, in a telephone network of Japan, instead of making such a setting, makes it possible to perform a communication of not notifying a telephone number of a caller device to a callee device, namely, the anonymous communication. Further, adopting the caller number notification as the default setting at the time of a contract, or affixing “186” to the head of a destination telephone number and dialing up with the caller device, for example, in a telephone network of Japan, instead of making such a setting, makes it possible to notify a telephone number of the caller device to the callee device.
Further, the specific number notification service described in Non-patent literature 2 is also one kind of the anonymous communications. In this specific number notification service, when the caller becomes a contractor of the specific number notification service, not a separate telephone number of the caller device but a receiving charge telephone number (one kind of representative numbers) contracted by the caller can be notified to the callee device.